Current man-down detection is accomplished by tracking a worker's movements over a period of time and determining whether sufficient motion has occurred to infer that the worker has not become incapacitated. The worker's movements are measured using an accelerometer or other motion measuring means carried within a first safety device that is carried by the worker or attached to their clothing.
For example, the motion measuring means could be a 3 axis accelerometer carried within a first safety device (such as a portable gas detector) attached to the worker's belt or clothing. The accelerometer triggers when an adjustable amount of time passes without any movement. The detector starts to emit an audio warning to give the user time to disarm the alarm. If the user does not disarm the alarm in time, the device then goes into its alarm mode and reports the error to a monitoring site.
Known solutions suffer from various drawbacks. For example, under general use, the device may register no movement even when there is no emergency. This causes the user to frequently disarm the countdown and becomes a nuisance. In addition, in the course of a day, the user may go on a break and leave the detector in a locker, car seat, table, etc. causing the detector to go into alarm. It is not usual procedure to require that the detector be turned off when not in use, as the expectation is that a detector can last at least a complete shift. It would be desirable to reduce false positive man down alarms.